This is your brain on poker

Researchers got subjects to bet against computers while inside an MRI tube.

Is it worth bluffing if you're playing cards against a computer? Most of us go through the day reading subtle (and some not-so-subtle) social cues, like tone of voice, body language, and facial expressions, to figure out what an appropriate course of action should be. To look into how humans read some of these social cues, researchers have put subjects into an MRI tube and asked them to play a simplified form of poker (just one card) against both computerized and human opponents.

The participants kept track of their opponents' behavior on previous trials when determining whether to bluff with a given card, but were more careful to pay attention to what their human opponents did. The researchers then used MRI images of brain activity to look for areas of the brain that might mediate this difference. One area stood out: the temporal-parietal junction, or TPJ.

(Functional MRI studies have come in for some criticism because the researchers often focus imaging on areas they expect to see involved. In this case, the researchers imaged the whole brain, divided it up evenly, and repeated the search for elevated activity. The TPJ still stood out.)

Surveying the participants, the authors discovered that the enhanced activity was only present in the TPJ when the card player thought that a human opponent was especially good at the game. Oddly, the TPJ had not been implicated in social interactions previously, and other regions that had already been shown to mediate social interactions didn't stand out at all in this context. But there's a lot that goes into deciding an opponent is tough and trying to infer how they'll respond, so it's not quite clear what this brain region is up to.

What is clear is that this is probably not the last game of poker that will be taking place inside a very expensive piece of imaging equipment.